A fraction collector is a device used for dispensing a flow of liquid in a number of receptacles where the receptacles are fed towards a dispensing means by means of a relative movement in one or two directions. As the droplets dispensed can have a diameter of 4 millimeters and the smallest receptacles have an orifice of 6.7 millimeters it is important that the receptacles are held in exactly the right position to avoid spilling. In a fraction collector used e.g. in an HPLC (High Pressure Liquid Chromatography) system it is important that different types of receptacles can be used. Thus the receptacles can consist e.g. of test tubes of various sizes or micro titer plates. This flexibility can be achieved by using a cassette tray onto which various types of cassettes for various types of receptacles can be loaded. The various types of cassettes are provided with some type of identification means so that the fraction collector can read e.g. the size of the test tubes and make the correct positioning of the dispensing means.
However, taking into account the small dimensions it is of great importance that said cassettes are positioned with very high accuracy, but at the same time the positioning of the cassettes in the fraction collector must be user friendly and not impose any additional action to ensure proper alignment.